Predicting the Impacts of Land Cover Management Scenarios on the Run-off Volume and River Pollutants Using the L-THIA Model for the Hablehrud basin

Land cover change is an important factor in terms of its impacts on altering the quantity and quality of the flow regimes. The Long-term Hydrologic Impact Assessment model was used to predict the impacts of land cover management scenarios on run-off volume and water pollutants on the Hablehrud Basin. Land-use and soil hydrologic group layers were used in running the model. Evaluation of the results indicated a satisfactory performance at the 5% level of significance. Additionally, the model uncertainty analysis was conducted using the bootstrap method. Nitrate, nitrite and run-off volume parameters had the minimum and maximum uncertainty levels with respect to the coefficient of variation at 0.15 and 0.26, respectively. In addition to the current condition, agroforestry, seeding, drill seeding, hill-drop planting, grazing exclusion, haloxylon plantation, orchard stabilization, tree plantation and forage growing actions were evaluated. By applying the seeding scenario, the annual runoff volume would drop from 301.07 million cubic meters per year for the current land use in the watershed to 247.92 million cubic meters per year. Given the seeding scenario, the total amounts of nitrates, nitrite and phosphorus in the watershed would also decrease from 214.17 and 92.4 ton per year for the current land cover to 154.2 and 80.3 ton per year, respectively. Evaluation of the results indicates the satisfactory performance of the model to predict the effects of land-use change scenarios in this area. Implementing the land cover management actions leads to a reduction in the run-off volume as well as the water pollutants on the Hablerud Basin.